Effect of powder particle size on wear resistance of plasma sprayed molybdenum coating

Abstract

Plasma-sprayed molybdenum coatings are used in automotive, aerospace, pulp and paper industries in order to guard the machine parts against wear and corrosion. In this work, an attempt has been made to study the effect of particle size on wear behaviour of molybdenum coated steel. Two types of Mo coatings were deposited on American Iron and Steel Institute (AISI) 1020 steel substrate, one is with particle size of 15–40 µm (type I) and another one is with 40–90 µm (type II) using plasma spraying. The microstructures and worn surface morphologies of the coatings were analysed by means of X-ray diffractometer and scanning electron microscopy. It was found that the as-sprayed type I and type II coatings consist of molybdenum (Mo) as the major phase and molybdenum oxide (MoO2) as the minor phases. For the evaluation of influence of coating powder particle size on wear characteristics, the sliding wear tests were performed on a pin-on-disc apparatus. The variation of volume loss with applied load, sliding speed and sliding distance was monitored. The type I sprayed coating exhibits better wear resistance. Tribological testing was also supported by metallographic examination for the identification of wear mechanisms. It was verified that the wear of coating is dominated by fracture of splats, crack propagation, delamination and plowing.